Electrostatic dissipative TPU and compositions thereof

ABSTRACT

The present invention relates to an electrostatic dissipative thermoplastic polyurethane composition made by reacting (a) at least one polyester polyol intermediate with (b) at least one diisocyanate and (c) at least one chain extender. The polyester polyol intermediate, may be derived from at least one dialkylene glycol and at least one dicarboxylic acid, or an ester or anhydride thereof. The invention further provides for methods of making said thermoplastic polyurethane composition, polymer blends containing said thermoplastic and polymer articles made from said thermoplastic.

CROSS REFERENCE

This application claims priority from Provisional Application Ser. No.61/251,782 filed on Oct. 15, 2009.

BACKGROUND OF THE INVENTION

The present invention relates to electrostatic dissipative thermoplasticurethanes (TPU) and compositions thereof.

The formation and retention of charges of static electricity on thesurface of most plastics is well known. Many plastic materials have asignificant tendency to accumulate static electrical charges due to lowelectrical conductivity. This type of formation and retention of chargesof static electricity can be problematic. The presence of staticelectrical charges on sheets of thermoplastic film, for example, cancause the sheets to adhere to one another thus making their separationfor further processing more difficult. Moreover, the presence of staticelectrical charges causes dust to adhere to items packaged in a plasticbag for example, which may negate any sales appeal.

The increasing complexity and sensitivity of microelectronic devicesmakes the control of static discharge of particular concern to theelectronics industry. Even a low voltage discharge can cause severedamage to sensitive devices. The need to control static charge buildupand dissipation often requires the entire assembly environment for thesedevices to be constructed of partially conductive materials and/orelectrostatic discharge (ESD) materials. It also may require thatelectrostatic protective packages, tote boxes, casings, and covers bemade from conductive polymeric materials to store, ship, protect, orsupport electrical devices and equipment.

The prevention of the buildup of static electrical charges whichaccumulate on plastics during manufacture or use has been accomplishedby the use of various ESD additives such as antistatic agents and ESDingredients. These additives can be applied as a coating which may besprayed or dip coated on the article after manufacture, although thismethod usually results in a temporary solution. Alternatively, thesematerials can be incorporated into a polymer used to make the articleduring processing, thereby providing a greater measure of permanence.

However, the incorporation of such ESD materials (ESD and/or antistaticagents) presents serious problems. For example, the high temperaturesrequired for conventional processing of most polymers will often damageor destroy antistatic agents. Moreover, many ESD agents are not misciblewith the matrix or base polymers in which they are used. These issuescan lead to reduced moldability of the polymer, or blends containing thepolymer, as the antistatic agents can migrate or diffuse to the surfaceduring processing and deposit a coating on mold surfaces, possiblydestroying the surface finish on the manufactured part being molded. Insevere cases, the surface of the article becomes oily and marbleized. Alarge number of antistatic agents are also either cationic or anionic innature. These agents tend to cause the degradation of plastics,particularly PVC, and result in discoloration or loss of physicalproperties. Additional problems which can occur with ESD agents includeloss of their ESD capability due to evaporation, wear and rinsing, thedevelopment of undesirable odors, and the promotion of stress crackingor crazing on the surface of an article in contact with the article ofmanufacture. ESD agents may also be very sensitive to moisture, leadingto reduced effectiveness in applications that expose the agent to water.

There are several examples of high molecular weight ESD agents in theprior art. In general, these additives have been high molecular weightpolymers of ethylene oxide or similar materials like propylene oxide,epichlorohydrin, glycidyl ethers, and the like. It has been arequirement that these additives be high molecular weight materials toovercome the problems related to the migration, evaporation and/or thethermal stability of the ESD additive. However, these prior art ESDadditives do not have a desired balance between electrical conductivityand acceptable low levels of extractable anions, in particular chloride,nitrate, phosphate, and sulfate, which in turn can cause anymanufactured articles containing such ESD additives to have unacceptableproperties for some end uses.

In addition, there are examples in the art of certain polyetherthermoplastic urethanes that have good ESD properties, with and withoutthe use of antistatic agents. However, polyether TPU compositionsgenerally have poor properties including poor phase separationcharacteristics, difficulties achieving high molecular weights,inadequate compatibility with many other types of host polymersresulting in poor physical properties, and poor heat performance makingthem unsuitable for many applications. Polyester TPU compositionsgenerally have better physical properties, but poor ESD properties.There is a need for TPU compositions that possess both the ESDproperties of polyether TPU compositions and the physical properties ofpolyester TPU compositions.

SUMMARY OF THE INVENTION

The present invention provides an electrostatic dissipativethermoplastic polyurethane (ESD-TPU) composition made by reacting (a) atleast one polyester polyol intermediate with (b) at least onediisocyanate and (c) at least one chain extender. The polyester polyolintermediate may be derived from at least one dialkylene glycol and atleast one dicarboxylic acid, or an ester or anhydride thereof. Thepresent invention also provides a process of making such ESD-TPUpolymers and compositions thereof.

The compositions of the present invention may further comprise aneffective amount of a metal containing salt for acceptable electrostaticdissipation properties.

The compositions of the present invention may be a polymer blendcomprising the ESD-TPU compositions described herein mixed with at leastone polymer base.

The present invention also provides shaped polymeric articles where thearticles comprise the ESD-TPU compositions described herein.

DETAILED DESCRIPTION OF THE INVENTION

Various features and embodiments of the invention will be describedbelow by way of non-limiting illustration.

The Electrostatic Dissipative Thermoplastic Polyurethane.

The electrostatic dissipative thermoplastic polyurethane (ESD-TPU)polymers used in this invention are made by reaction of three reactants.The first reactant is a polyester polyol intermediate, the secondreactant is a diisocyanate, and the third reactant is a chain extender.Each of the three reactants is discussed below.

The ESD-TPU polymer and/or compositions thereof of the present inventionhave dramatically improved ESD properties compared to conventionalpolyester polyol-derived TPU polymers, and may also have improvedphysical properties and/or improved ionic cleanliness propertiescompared to conventional polyether polyol-derived TPU polymers. In oneembodiment, the ESD-TPU polymer and/or compositions thereof of thepresent invention have ESD properties at least comparable toconventional polyether polyol-derived TPU polymers and/or compositionsthereof while also having physical properties and/or ionic cleanlinessproperties at least comparable to conventional polyester polyol-derivedTPU polymers and/or compositions thereof

In some embodiments, the ESD-TPU polymer compositions of the presentinvention have a surface resistivity of no more than, or below, 1.0×10¹³ohm/square, and/or a volume resistivity of no more than, or below,1.0×10¹² ohm-centimeter, as measured by ASTM D-257. In otherembodiments, the ESD-TPU polymer compositions have a surface resistivityof no more than, or below, 1.0×10¹¹ ohm/square, and/or a volumeresistivity of no more than, or below, 1.0×10¹¹ ohm-centimeter.

The ESD-TPU polymer compositions may also have a static decay rate ofless than about 1 second, or about 0.1 seconds from 1000 V to 100 V asmeasured at 50% relative humidity using a charged plate monitor, and/ora static decay rate of less than about 1 second, or about 0.1 secondsfrom 5000 V to 50 V or from −5000 V to −50 V, as measured at 12%relative humidity, by FTMS 101C.

The ESD-TPU polymer compositions may also possess one or more of thephysical properties described below, including embodiments incombination with one or more of the ESD properties described above. Thecomposition may have a hardness of at least 60 or 70 Shore A units, asmeasured by ASTM D-2240. The composition may have a tensile strength ofat least 10, 15, 17 or even 17.9 MPa and an ultimate elongation of morethan 300%, 500% or even 600% as measured by ASTM D-412. The compositionmay have a Graves tear value of at least 5, or 5.6 kg/mm, as measured byASTM D-624, using die C. The composition may have a Taber loss, perCS-17/1000 revolutions, of not more than, or less than, 100, 50, 40, oreven 35 mg, as measured by ASTM D-3389 or D4060-95. The composition mayhave a weight average molecular weight of from 60,000 to 500,000 or from80,000 to 300,000. The composition may have a melt flow index of lessthan 50, 40 or even 35 grams per 10 minutes, as measured by ASTM D-1238Procedure A at a barrel temperature of 190° C. and a 3.8 kg piston load.

In some embodiments, the present invention also solves the problem ofobtaining ESD polymers without also having unacceptably high levels ofextractable anions, in particular chloride, nitrate, phosphate,fluoride, bromide, and sulfate anions and ammonium cations. In suchembodiments, the ESD TPU polymer and/or compositions thereof have lessthan about 8,000 parts per billion (ppb) total extractable anionsmeasured from the group of all six of chloride anions, nitrate anions,phosphate anions, fluoride anions, bromide anions, and sulfate anions,and less than about 1,000 ppb of said chloride anions, less than about100 ppb of said nitrate anions, less than about 6,000 ppb of saidphosphate anions, and less than about 1,000 ppb of said sulfate anions.

The Polyester Polyol Intermediate.

The polyester polyol intermediate of the present invention is derivedfrom at least one dialkylene glycol and at least one dicarboxylic acid,or an ester or anhydride thereof.

The polyester polyol intermediates of the present invention may includeat least one terminal hydroxyl group, and in some embodiments, at leastone terminal hydroxyl group and one or more carboxylic acid groups. Inanother embodiment, the polyester polyol intermediates include twoterminal hydroxyl groups, and in some embodiments, two hydroxyl groupsand one or more, or two, carboxylic acid groups. The polyester polyolintermediates are generally a substantially linear, or linear, polyesterhaving a number average molecular weight (Mn) of from about 500 to about10,000, about 500 to about 5000, or from about 1000 to about 3000, orabout 2000.

In some embodiments, the polyester polyol intermediate may have a lowacid number, such as less than 1.5, less than 1.0, or even less than0.8. A low acid number for the polyester polyol intermediate maygenerally provide improved hydrolytic stability in the resulting TPUpolymer. The acid number may be determined by ASTM D-4662 and is definedas the quantity of base, expressed in milligrams of potassium hydroxidethat is required to titrate acidic constituents in 1.0 gram of sample.Hydrolytic stability can also be improved by adding hydrolyticstabilizers to the TPU which are known to those skilled in the art offormulating TPU polymers.

Dialkylene glycols suitable for use in preparing the polyester polyolintermediate of the present invention may be aliphatic, cyclo-aliphatic,aromatic, or combinations thereof. Suitable glycols may contain from 2or 4 or 6 to 20, 14, 8, 6 or 4 carbon atoms, and in some embodiments maycontain 2 to 12, 2 to 8 or 6, 4 to 6, or even 4 carbon atoms. In someembodiments, the dialkylene glycol includes oxydimethanol, diethyleneglycol, dipropylene glycol, 3,3-oxydipropan-1-ol, dibutylene glycol, orcombinations thereof. In other embodiments, one or more of thedialkylene glycols listed may be excluded from the present invention.Blends of two or more glycols may be used. In some embodiments,monoalkylene glycols may be used in combination with the dialkyleneglycols described above. In other embodiments, the glycol used toprepare the polyester polyol intermediate is free of monoalkyleneglycols.

Dicarboxylic acids suitable for use in preparing the polyester polyolintermediate of the present invention may be aliphatic, cyclo-aliphatic,aromatic, or combinations thereof. Suitable acids may contain from 2, 4,or 6 to 20, 15, 8, or 6 carbon atoms, and in some embodiments maycontain 2 to 15, 4 to 15, 4 to 8, or even 6 carbon atoms. In someembodiments, the dicarboxylic acids include succinic acid, glutaricacid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacicacid, dodecanedioic acid, isophthalic acid, terephthalic acid,cyclohexane dicarboxylic acid, or combinations thereof. In otherembodiments, one or more of the dicarboxylic acids listed may beexcluded from the present invention.

The polyester polyol intermediates of the present invention may also bederived from an ester or anhydride of one or more the dicarboxylic acidsdescribed above or combinations of such materials. Suitable anhydridesinclude succinic anhydride, alkyl and/or alkenyl succinic anhydride,phthalic anhydride and tetrahydrophthalic anhydride. In someembodiments, the acid is adipic acid. Blends of two or more acids may beused.

The polyester polyol intermediates of the present invention are preparedby reacting one or more of the dialkylene glycol described above withone or more of the dicarboxylic acids described above, and/or one ormore of the esters or anhydrides thereof. In some embodiments, more thanone equivalent of glycol is used for each equivalent of acid. Thepreparation includes (1) an esterification reaction of one or moredialkylene glycols with one or more dicarboxylic acids or anhydrides or(2) by transesterification reaction, i.e., the reaction of one or moredialkylene glycols with esters of dicarboxylic acids. Mole ratiosgenerally in excess of more than one mole of glycol to acid arepreferred so as to obtain linear chains having a preponderance ofterminal hydroxyl groups.

In some embodiments, the polyester polyol intermediate of the presentinvention is used in combination with one or more polyether polyolintermediates and/or polyester polyol intermediates (that is one or morepolyester polyol intermediates derived from polyols other than thosedescribed above). As used herein, the polyester polyol intermediates ofthe present invention may include a mixture of polyester and polyetherlinkages, but may not contain only polyether linkages or, in someembodiments, more than 70% polyether linkages. In other embodiments, thecompositions of the present invention are substantially free, or freeof, polyether polyol intermediates, and such materials are not used inthe preparation, where polyether polyol intermediates as used herein canmean intermediates containing only polyether linkages, or containingless than 50, 40, 20, or even 15 percent polyester linkages.

The Diisocyanate.

The second reactant to make the ESD-TPU of this invention is adiisocyanate. Suitable diisocyanates include: (i) aromatic diisocyanatessuch as: 4,4′-methylenebis-(phenyl isocyanate) (MDI), m-xylylenediisocyanate (XDI), phenylene-1,4-diisocyanate, 1,5-naphthalenediisocyanate, diphenylmethane-3,3′-dimethoxy-4,4′-diisocyanate (TODI),and toluene diisocyanate (TDI); as well as (ii) aliphatic diisocyanatessuch as: isophorone diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate(CHDI), decane-1,10-diisocyanate, hexamethylene diisocyanate (HDI), anddicyclohexylmethane-4,4′-diisocyanate. In some embodiments, thediisocyanate is 4,4′-methylenebis(phenyl isocyanate) (MDI). In otherembodiments, one or more of the diisocyanates listed may be excludedfrom the present invention.

A mixture of two or more diisocyanates can be used. Also, small amountsof isocyanates having a functionality greater than 2, such astri-isocyanates can be used together with the diisocyanates. Largeamounts of isocyanates with a functionality of 3 or more should beavoided as they will cause the TPU polymer to be cross linked.

The Chain Extender.

Suitable chain extenders include glycols and can be aliphatic, aromaticor combinations thereof. In some embodiments, the chain extenders areglycols having from 2 to about 12 carbon atoms.

In some embodiments, the glycol chain extenders are lower aliphatic orshort chain glycols having from about 2 to about 10 carbon atoms andinclude, for instance: ethylene glycol, diethylene glycol, propyleneglycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol,1,3-butanediol, 1,5-pentanediol, 1,4-cyclohexanedimethanol,neopentyglycol, and the like. In some embodiments, the chain extenderincludes 1,4-butanediol.

Aromatic glycols may also be used as the chain extender to make the TPUincluding benzene glycol and xylene glycol. Xylene glycol is a mixtureof 1,4-di(hydroxymethyl)benzene and 1,2-di(hydroxymethyl)benzene.Benzene glycol specifically includes hydroquinone,bis(beta-hydroxyethyl)ether also known as1,4-di(2-hydroxyethoxy)benzene; resorcinol, bis(beta-hydroxyethyl)etheralso known as 1,3-di(2-hydroxyethyl)benzene; catechol,bis(beta-hydroxyethyl)ether also known as1,2-di(2-hydroxyethoxy)benzene; and combinations thereof.

A mixture of two or more glycols may be used as the chain extender inESD-TPU of this invention. In some embodiments, the chain extender is amixture of 1,4-butanediol and 1,6-hexanediol. In other embodiments, oneor more of the chain extenders listed may be excluded from the presentinvention.

Diamines may also be used as a chain extender, as is well known in theart. In one embodiment of the present invention, the chain extendercontains a diamine as a co-chain extender in combination with one ormore of the chain extenders described above. In other embodiments thepresent invention does not use any diamines in the preparation of itscompositions.

The Process of Making the TPU.

The three reactants (the polyester polyol intermediate, thediisocyanate, and the chain extender) are reacted together to form thehigh molecular weight ESD-TPU of this invention. Any known processes toreact the three reactants may be used to make the TPU. In oneembodiment, the process is a so-called “one-shot” process where allthree reactants are added to an extruder reactor and reacted. Theequivalent weight amount of the diisocyanate to the total equivalentweight amount of the hydroxyl containing components, that is, thepolyester polyol intermediate and the chain extender glycol, can be fromabout 0.95 to about 1.10, or from about 0.96 to about 1.02, and evenfrom about 0.97 to about 1.005. Reaction temperatures utilizing aurethane catalyst can be from about 175 degrees C. to about 245 degreesC., and in other embodiment from 180 degrees C. to 220 degrees C.

Generally, any conventional catalyst can be utilized to react thediisocyanate with the polyester polyol intermediates or the chainextender. Examples of suitable catalysts include the various alkylamines, alkyl ethers or alkyl thiol ethers of bismuth or tin wherein thealkyl portion has from 1 to about 20 carbon atoms with specific examplesincluding bismuth octoate, bismuth laurate, and the like. Preferredcatalysts include the various tin catalysts such as stannous octoate,dibutyltin dioctoate, dibutyltin dilaurate, and the like. The amount ofsuch catalyst is generally small, such as from about 20 to about 200parts per million based upon the total weight of the polyurethaneforming reactants.

The ESD-TPU can also be prepared utilizing a pre-polymer process. In thepre-polymer route, the polyester polyol intermediates are reacted withgenerally an equivalent excess of one or more diisocyanates to form apre-polymer solution having free or unreacted diisocyanate therein. Thereaction is generally carried out at temperatures of from about 80degrees C. to about 220 degrees C., or from about 150 degrees C. toabout 200 degrees C. in the presence of a suitable urethane catalyst.Subsequently, a chain extender, as noted above, is added in anequivalent amount generally equal to the isocyanate end groups as wellas to any free or unreacted diisocyanate compounds. The overallequivalent ratio of the total diisocyanate to the total equivalent ofthe hydroxyl terminated polyesters and the chain extender is thus fromabout 0.95 to about 1.10, or from about 0.96 to about 1.02 and even fromabout 0.97 to about 1.05. The chain extension reaction temperature isgenerally from about 180 degrees C. to about 250 degrees C., or fromabout 200 degrees C. to about 240 degrees C. Typically, the pre-polymerroute can be carried out in any conventional device including anextruder. In such embodiments, the polyester polyol intermediates arereacted with an equivalent excess of a diisocyanate in a first portionof the extruder to form a pre-polymer solution and subsequently thechain extender is added at a downstream portion and reacted with thepre-polymer solution. Any conventional extruder can be utilized,including extruders equipped with barrier screws having a length todiameter ratio of at least 20 and in some embodiments at least 25.

In one embodiment, the ingredients are mixed in a single or twin screwextruder with multiple heat zones and multiple feed ports between itsfeed end and its die end. The ingredients may be added at one or more ofthe feed ports and the resulting ESD-TPU composition that exits the dieend of the extruder may be pelletized.

In some embodiments, component (a), the polyester polyol intermediateincludes poly(diethylene glycol adipate), component (b), thediisocyanate includes 4,4′-methylenebis-(phenyl isocyanate), andcomponent (c), the chain extender includes butanediol, HQEE(hydroquinone bis(2-hydroxyethyl)ether), or combinations thereof.

The Metal Containing Salt.

In some embodiments, the compositions of the present invention mayfurther comprise a metal-containing salt, salt complex, or salt compoundformed by the union of metal ion with a non-metallic ion or molecule.The amount of salt present may be an amount effective to provideimproved ESD properties to the ESD-TPU polymer and/or the overallcomposition. The optional salt component may be added during theone-shot polymerization process. The salt may be a lithium containingsalt.

While the exact mechanism of attachment and/or attraction of the salt tothe ESD-TPU polymer reaction product is not completely understood, thesalt can unexpectedly improve the surface and volume resistivities ofthe resulting polymer, and may accomplish this without the presence ofunacceptably high levels of extractable anions. Moreover, the staticdecay times remain in an acceptable range, that is, the times are nottoo fast or too slow.

Examples of salts useful in the present invention include: LiClO₄,LiN(CF₃SO₂)₂, LiPF₆, LiAsF₆, Lil, LiCl, LiBr, LiSCN, LiSO₃ CF₃, LiNO₃,LiC(SO₂CF₃)₃, Li₂S, and LiMR₄, where M is Al or B, and R is a halogen,hydrocarbyl, alkyl or aryl group. In one embodiment, the salt is LiN(CF₃ SO₂)₂, which is commonly referred to as lithium trifluoromethanesulfonimide (but which is also sometimes referred to as lithiumtrifluoromethane sulfonamide even though it has a imide structure), orthe lithium salt of trifluoromethane sulfonic acid. The effective amountof the selected salt added to the one-shot polymerization may be atleast about 0.10, 0.25, or even 0.75 parts by weight based on 100 partsby weight of the polymer.

In some embodiments, the compositions of the present invention furthercomprises a sulfonate-type anionic antistatic agent. Suitable examplesinclude metal alkylsulfonates and metal alkyl-aromatic sulfonates. Themetal alkylsulfonates can include, alkali metal or alkaline earth metalaliphatic sulfonates in which the alkyl group has 1 to 35 or 8 to 22carbon atoms. The alkali metals may include sodium and potassium and thealkaline earth metals may include calcium, barium and magnesium.Specific examples of metal alkylsulfonates include sodiumn-hexylsulfonate, sodium n-heptylsulfonate, sodium n-octylsulfonate,sodium n-nonylsulfonate, sodium n-decylsulfonate, sodiumn-dodecylsulfonate, sodium n-tetradecylsulfonate, sodiumn-hexadecylsulfonate, sodium n-heptadecylsulfonate and sodiumn-octadecylsulfoante. Specific examples of metal alkyl-aromaticsulfonates include alkali metal or alkaline earth metal salts ofsulfonic acids comprising 1 to 3 aromatic nuclei substituted with analkyl group having 1 to 35 or 8 to 22, carbon atoms. The aromaticsulfonic acids include, for example, benzenesulfonic,naphthalene-1-sulfonic, naphthalene-2,6-disulfonic, diphenyl-4-sulfonicand diphenyl ether 4-sulfonic acids. Metal alkyl-aromatic sulfonatesinclude, for example, sodium hexylbenzenesulfonate, sodiumnonylbenzenesulfonate and sodium dodecylbenzenesulfonate.

The compositions of the present invention may also include an non-metalcontaining anti-stat additives, such as ionic liquids. Suitable liquidsinclude tri-n-butylmethylammonium bis-(trifluoroethanesulfonyl)imide(available as FC-4400 from 3M™), and similar materials.

In some embodiments, the present invention allows for the use ofco-solvent with the metal containing salt. The use of a co-solvent may,in some embodiments, allow a lower charge of salt to provide the samebenefit in ESD properties. Suitable co-solvents include ethylenecarbonate, propylene carbonate, dimethyl sulfoxide, tetramethylenesulfone, tri- and tetra ethylene glycol dimethyl ether, gammabutyrolactone, and N-methyl-2-pyrrolidone. When present, the co-solventmay be used at least about 0.10, 0.50 or even 1.0 parts by weight basedon 100 parts by weight of the polymer. In some embodiments, thecompositions of the present invention are substantially free to free ofany or all of the co-solvents described herein.

In other embodiments, the compositions of the present invention aresubstantially free to free of any or all of the metal containing saltsdescribed herein.

Additional Additives.

The compositions of the present invention may further include additionaluseful additives, where such additives can be utilized in suitableamounts. These optional additional additives include opacifyingpigments, colorants, mineral and/or inert fillers, stabilizers includinglight stabilizers, lubricants, UV absorbers, processing aids,antioxidants, antiozonates, and other additives as desired. Usefulopacifying pigments include titanium dioxide, zinc oxide, and titanateyellow. Useful tinting pigments include carbon black, yellow oxides,brown oxides, raw and burnt sienna or umber, chromium oxide green,cadmium pigments, chromium pigments, and other mixed metal oxide andorganic pigments. Useful fillers include diatomaceous earth (superfloss)clay, silica, talc, mica, wallostonite, barium sulfate, and calciumcarbonate. If desired, useful stabilizers such as antioxidants can beused and include phenolic antioxidants, while useful photostabilizersinclude organic phosphates, and organotin thiolates (mercaptides).Useful lubricants include metal stearates, paraffin oils and amidewaxes. Useful UV absorbers include 2-(2′-hydroxyphenyl) benzotriazolesand 2-hydroxybenzophenones. Additives can also be used to improve thehydrolytic stability of the TPU polymer. Each of these optionaladditional additives described above may be present in, or excludedfrom, the compositions of the present invention.

When present, these additional additives may be present in thecompositions of the present invention from 0 or 0.01 to 5 or 2 weightpercent of the composition. These ranges may apply separately to eachadditional additive present in the composition or to the total of alladditional additives present.

Polymer Containing Blends.

The ESD-TPU polymers of the present invention may be blended with amatrix or base polymer to form a polymer blend. These blends may also bemade with the salt-modified ESD-TPU polymers described above.

Suitable base polymers as defined herein can be a homopolymer or acopolymer. The base polymer may be a blend of multiple base polymers,and may further include any of the additional additives described above,including ESD additives. In some embodiments, the base polymer and/orthe compositions of the present invention are substantially free to freeof ESD additives.

The base polymer may include:

(i) a polyolefin (PO), such as polyethylene (PE), polypropylene (PP),polybutene, ethylene propylene rubber (EPR), polyoxyethylene (POE),cyclic olefin copolymer (COC), or combinations thereof;

(ii) a styrenic, such as polystyrene (PS), acrylonitrile butadienestyrene (ABS), styrene acrylonitrile (SAN), styrene butadiene rubber(SBR or HIPS), polyalphamethylstyrene, methyl methacrylate styrene (MS),styrene maleic anhydride (SMA), styrene-butadiene copolymer (SBC) (suchas styrene-butadiene-styrene copolymer (SBS) andstyrene-ethylene/butadiene-styrene copolymer (SEBS)),styrene-ethylene/propylene-styrene copolymer (SEPS), styrene butadienelatex (SBL), SAN modified with ethylene propylene diene monomer (EPDM)and/or acrylic elastomers (for example, PS-SBR copolymers), orcombinations thereof;

(iii) a thermoplastic polyurethane (TPU);

(iv) a polyamide, such as Nylon™, including polyamide 6,6 (PA66),polyamide 1,1 (PA11), polyamide 1,2 (PA12), a copolyamide (COPA), orcombinations thereof;

(v) an acrylic polymer, such as polymethyl acrylate,polymethylmethacrylate, or combinations thereof;

(vi) a polyvinylchloride (PVC), a chlorinated polyvinylchloride (CPVC),or combinations thereof;

(vii) a polyoxymethylene, such as polyacetal;

(viii) a polyester, such as polyethylene terephthalate (PET),polybutylene terephthalate (PBT), copolyesters and/or polyesterelastomers (COPE) including polyether-ester block copolymers such asglycol modified polyethylene terephthalate (PETG) polylatic acid (PLA),or combinations thereof;

(ix) a polycarbonate (PC), a polyphenylene sulfide (PPS), apolyphenylene oxide (PPO), or combinations thereof;

or combinations thereof.

Polyvinyl chloride (PVC), vinyl polymer, or vinyl polymer material, asused herein, refers to homopolymers and copolymers of vinyl halides andvinylidene halides and includes post halogenated vinyl halides such asCPVC. Examples of these vinyl halides and vinylidene halides are vinylchloride, vinyl bromide, vinylidene chloride and the like. The vinylhalides and vinylidene halides may be copolymerized with each other oreach with one or more polymerizable olefinic monomers having at leastone terminal CH₂═C<grouping. As examples of such olefinic monomers theremay be mentioned the alpha,beta-olefinically unsaturated carboxylicacids, such as acrylic acid, methacrylic acid, ethyl acrylic acid,alpha-cyano acrylic acid, and the like; esters of acrylic acid, such asmethyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate,cyanoethyl acrylate, hydroxyethyl acrylate, and the like; esters ofmethacrylic acid, such as methyl methacrylate, butyl methacrylate,hydroxyethyl methacrylate, and the like; nitriles, such asacrylonitrile, methacrylonitrile, and the like; acrylamides, such asmethyl acrylamide, N-methylol acrylamide, N-butyoxy methylacrylamide,and the like; vinyl ethers, such as ethyl vinyl ether, chloroethyl vinylether, and the like; the vinyl ketones; styrene and styrene derivatives,such as .alpha.-methyl styrene, vinyl toluene, chlorostyrene, and thelike; vinyl naphthalene, allyl and vinyl chloroacetate, vinyl acetate,vinyl pyridine, methyl vinyl ketone; the diolefins, including butadiene,isoprene, chloroprene, and the like; and other polymerizable olefinicmonomers of the types known to those skilled in the art. In oneembodiment, the base polymer includes polyvinyl chloride (PVC) and/orpolyethylene terephthalate (PET).

Industrial Application

The compositions of the present invention, including the blendsdescribed above, are useful for a variety of applications. Some examplesare tubes, paper trays, floor tiles, machine housings, construction andmanufacturing equipment, and polymeric sheets and films. Morespecifically, examples include fuel handling equipment such as fuellines and vapor return equipment, business equipment, coatings forfloors such as for clean rooms and construction areas, applications,clean room equipment including garments, floorings, mats, electronicpackaging, and housings, chip holders, chip rails, tote bins and totebin tops, medical applications, battery parts such as dividers and/orseparators, and generally shaped articles.

In one embodiment, the compositions of the present invention are used tomake polymeric articles to be used as: packaging materials forelectronic parts; internal battery separators for use in theconstruction of lithium-ion batteries; clean room supplies andconstruction materials; antistatic conveyor belts; parts for officemachines; antistatic garments and shoes, or combinations thereof.

Electronic parts include ESD sensitive parts including semiconductors.The articles of the present invention may also be durable or consumableparts for clean room equipment and applications. Also included areconstruction and/or building materials for clean rooms and data centers,which may include items such as softwalls, curtains, flooring, benches,etc. The articles of the present invention also include laminatedsheets, conveyor belts for manufacturing of food, pharmaceuticalproducts, medical devices, and electronic components; or combinationsthereof.

Furthermore, the compositions of the present invention may be used toprepare separators and other components of lithium-ion batteries,lithium-polymer batteries and fuel cells. Such uses of the compositionsand articles of the present invention offer advantages over currentbatteries and fuel cells in the areas of improved safety, performance,cost, or combinations thereof. The compositions of the present inventionmay be used to construct separator layers that are placed between theanodes of the battery, as well as polymer electrolyte membranes.

The compositions can be used with various molding techniques includinginjection molding, compression molding, slush molding, extrusion,thermoforming cast, rotational molding, sintering, and vacuum molding.Articles of this invention may also be made from resins produced by thesuspension, mass, emulsion or solution processes.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. For instance,metal ions (of, e.g., a detergent) can migrate to other acidic oranionic sites of other molecules. The products formed thereby, includingthe products formed upon employing the composition of the presentinvention in its intended use, may not be susceptible of easydescription. Nevertheless, all such modifications and reaction productsare included within the scope of the present invention; the presentinvention encompasses the composition prepared by admixing thecomponents described above.

EXAMPLES

The invention will be further illustrated by the following examples,which sets forth particularly advantageous embodiments. While theexamples are provided to illustrate the present invention, they are notintended to limit it.

Example 1-A

An ESD TPU is prepared by reacting 4,4′-methylenebis-(phenylisocyanate), benzene glycol, and a polyester polyol intermediate derivedfrom diethylene glycol and adipic acid, in the manner described above,using the one shot process in the presence of a tin catalyst.

Example 1-B

An ESD TPU is prepared according to the procedure in Example 1-A exceptthat the TPU is doped, via wet absorption, with 1.9 parts per hundred(phr) of lithium trifluoromethane sulfonimide, a metal containing salt.

Example 1-C

An ESD TPU is prepared according to the procedure in Example 1-A exceptthat the TPU is doped, via wet absorption, with 1.4 phr of the lithiumsalt of trifluoromethane sulfonic acid, a metal containing salt.

Example 1-D

An ESD TPU is prepared according to the procedure in Example 1-A exceptthat the TPU is doped, via wet absorption, with 1.3 phr of the lithiumsalt of trifluoromethane sulfonic acid, a metal containing salt.

Example 2-A

An ESD TPU is prepared by reacting 4,4′-methylenebis-(phenylisocyanate), 1,4-butandiol, and a polyester polyol intermediate derivedfrom diethylene glycol and adipic acid, in the manner described above,using the one shot process in the presence of a tin catalyst.

Example 2-B

An ESD TPU is prepared according to the procedure in Example 2-A exceptthat the TPU is doped, via wet absorption, with 1.9 phr of lithiumtrifluoromethane sulfonimide, a metal containing salt.

Example 2-C

An ESD TPU is prepared according to the procedure in Example 2-A exceptthat the TPU is doped, via wet absorption, with 1.4 phr of the lithiumsalt of trifluoromethane sulfonic acid, a metal containing salt.

Comparative Example 3-A

A commercially available ESD polyether TPU is used for comparison to thecompositions of the present invention. This example is Stat-Rite™C-2300, an ESD polyether TPU available from the Lubrizol AdvancedMaterials, Inc.

The examples described above were tested to evaluate the ESD andphysical properties. The results of this testing is shown in the tablesbelow.

TABLE 1 Properties of Non-Doped TPUs Property Test¹ Ex 1-A Ex 2-A CompEx 3-A Hardness (5 sec), Shore A D2240 70 85 70 Specific Gravity D7921.23 1.24 1.20 Melting Point (Tm), degrees C. Internal 140 166 130 GlassTrans Pt (Tg), degrees C. −24 −22 −28 Tensile Strength, MPa D412 17.948.3 19.3 Ultimate Elongation, % 830 610 800 Tensile Stress at 100%, MPa3.4 6.6 Tensile Stress at 300%, MPa 5.5 11.0 Graves Tear Strength, kg/mmD624 5.6 9.1 4.7 (die C) Taber Loss (per 1000 rev), mg D3389 6 35 140(H18, 1 kg) Surface Resistivity, Ohm/sq D-257 2.6E+11 2.0E+12 3.9E+09Volume Resistivity, Ohm-cm (50% RH) 1.0E+11 9.0E+11 7.1E+09 ¹All testmethods are ASTM methods, except for the DSC testing which was completedinternally using a differential scanning calorimeter (DSC). Resistanceresults are formatted such that 1.0E+10 indicates a result of 1.0 × 10¹⁰and so on.

TABLE 2 ESD Properties of Non-Doped and Doped TPUs Surface Resistivity¹Volume Resistivity¹ Material (Ohm/sq) (Ohm-cm) Example 1-A 2.6E+111.0E+11 Example 1-B 1.2E+08 1.1E+07 Example 1-C 1.2E+08 3.8E+07 Example1-D 3.2E+08 7.8E+07 Example 2-A 2.0E+12 9.0E+11 Example 2-B 4.3E+091.4E+08 Example 2-C 1.1E+09 2.4E+08 Comp Ex 3-A 3.9E+09 7.1E+09 ¹ESDproperties are measured by ASTM D-257, at 50% relative humidity (RH).Resistance results are formatted such that 1.0E+10 indicates a result of1.0 × 10¹⁰ and so on.

The results show that the ESD TPU polymers of the present invention havephysical properties significantly better than the comparative ESDpolyether TPU. In addition, the non-doped ESD TPU compositions of thepresent invention have good ESD properties, comparable, if notequivalent to the ESD properties of the comparative ESD polyether TPUwhile the metal salt doped ESD TPU compositions of the present inventionprovide better ESD properties than the comparative ESD polyether TPU.

Example 1-D was tested to evaluate additional ESD properties. A summaryof these results is presented in the table below.

TABLE 3 ESD Properties of Example 1-D Property Test Example 1-D SurfaceResistivity, Ohm/sq D-257 3.9E+09 Volume Resistivity, Ohm-cm (50% RH)7.1E+09 Surface Resistance, Ohms ESD S11.11 3.3E+08 (12% RH) StaticDecay Time¹ FTMS-101C <0.1 sec +5000 V to +50 V (12% RH) −5000 V to −50V +1000 V to +100 V ¹Static decay rate measures the time it takes for anarticle made of the example material to discharge the indicated startingvoltage and reach the indicated ending voltage. The result is measuredin accordance with the FTMS-101C regulation.

Additional ESD TPU examples are also prepared, by in situpolymerization, as described below.

Example 4-A

An ESD TPU is prepared by in situ polymerization, combining 92.4 pbw ofa polyester polyol intermediate prepared from 1,4-butandiol and adipicacid, 92.4 pbw a polyester polyol intermediate prepared from diethyleneglycol and adipic acid, 14.2 pbw benzene glycol, 43.4 pbw4,4′-methylenebis-(phenyl isocyanate), 24.3 pbw lithium trifluoromethanesulfonimide, and 1 drop of tin octoate.

Example 4-B

An ESD TPU is prepared according to the procedure in Example 4-A exceptthat 73.0 pbw of an ionic liquid that containsbis(perfluoromethane)sulfonimide, alkyl ammonium salt is added to thematerial during processing.

Example 5-A

An ESD TPU is prepared by in situ polymerization, combining 92.4 pbw ofa polyester polyol intermediate prepared from 1,4-butandiol and adipicacid, 92.4 pbw a polyester polyol intermediate prepared diethyleneglycol and adipic acid, 14.2 pbw benzene glycol, 43.4 pbw4,4′-methylenebis-(phenyl isocyanate), and 0.75 pbw di-propylene glycol.

Example 5-B

An ESD TPU is prepared according to the procedure in Example 5-A exceptthat 2.0 pbw of lithium trifluoromethane sulfonimide is added to thematerial during processing. The salt is added during the one shotpolymerization of the TPU, as described above.

Example 5-C

An ESD TPU is prepared according to the procedure in Example 5-B exceptthat 3.0 pbw of lithium trifluoromethane sulfonimide is added to thematerial during processing.

Example 5-D

An ESD TPU is prepared according to the procedure in Example 5-B exceptthat 3.5 pbw of lithium trifluoromethane sulfonimide is added to thematerial during processing.

The examples described above were tested to evaluate their ESDproperties. The results of this testing is provided in the table below.

TABLE 4 ESD Properties of Non-Doped and Doped TPUs Surface Resistivity¹Volume Resistivity¹ Material (Ohm/sq) (Ohm-cm) Comp Ex 3-A 3.9E+097.1E+09 Example 4-A 1.4E+07 3.4E+06 Example 4-B 1.7E+06 1.3E+06 Example5-A 1.2E+11 Example 5-B 6.8E+08 Example 5-C 2.1E+08 Example 5-D 6.5E+08¹ESD properties are measured by ASTM D-257, at 50% relative humidity(RH).

The results show that the ESD TPU polymers of the present invention haveESD properties comparable to the comparative ESD polyether TPU. Theresults also show that when the ESD TPU polymers of the presentinvention further include a metal containing salt, the ESD properties ofthe compositions are improved to the point that they are better than thecomparative ESD polyether TPU.

Each of the documents referred to above is incorporated herein byreference. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about.” Unless otherwise indicated, all percent values, ppm values andparts values are on a weight basis. Unless otherwise indicated, eachchemical or composition referred to herein should be interpreted asbeing a commercial grade material which may contain the isomers,by-products, derivatives, and other such materials which are normallyunderstood to be present in the commercial grade. However, the amount ofeach chemical component is presented exclusive of any solvent or diluentoil, which may be customarily present in the commercial material, unlessotherwise indicated. It is to be understood that the upper and loweramount, range, and ratio limits set forth herein may be independentlycombined. Similarly, the ranges and amounts for each element of theinvention can be used together with ranges or amounts for any of theother elements. As used herein, the expression “consisting essentiallyof” permits the inclusion of substances that do not materially affectthe basic and novel characteristics of the composition underconsideration.

We claim:
 1. An electrostatic dissipative thermoplastic polyurethanecomposition made by reacting (a) at least one polyester polyolintermediate comprising poly(diethylene glycol adipate) with (b) atleast one diisocyanate comprising 4,4′-methylenebis-(phenyl isocyanate)and (c) at least one glycol chain extender comprising hydroquinonedi(hydroxyethyl) ether; wherein said electrostatic dissipativethermoplastic polyurethane composition further comprises an effectiveamount of a metal salt for electrostatic dissipation wherein said metalsalt is substantially free of any co-solvents and wherein the metal saltis not added to the electrostatic dissipative thermoplastic polyurethanecomposition in combination with a co-solvent; wherein said metal saltcomprises lithium trifluoromethane sulfonamide; and wherein saidelectrostatic dissipative thermoplastic polyurethane composition furthercomprises an antistatic agent comprising tri-n-butylmethylammoniumbis-(trifluororethanesulfonyl)imide.
 2. The composition of claim 1wherein (b), the diisocyanate, further comprises: hexamethylenediisocyanate, 3,3′-dimethylbiphenyl-4,4′-diisocyanate, m-xylylenediisocyanate, phenylene-1,4-diisocyanate, naphthalene-1,5-diisocyanate,diphenylmethane-3,3′-dimethoxy-4,4′-diisocyanate, toluene diisocyanate,isophorone diisocyanate, 1,4-cyclohexyl diisocyanate,decane-1,10-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, orcombinations thereof; and wherein (c), the chain extender, furthercomprises: ethylene glycol, diethylene glycol, propylene glycol,dipropylene glycol, 1,6-hexanediol, 1,3-butanediol, 1,5-pentanediol,1,4-cyclohexane-dimethanol, neopentyglycol, 1,4-bis(2-hydroxyethoxy)benzene, 1,4-butanediol, or combinations thereof.
 3. The composition ofclaim 1 wherein said composition has at least one of the followingcharacteristics: (i) the composition has a surface resistivity below1.0×10¹³ ohm/square and a volume resistivity below 1.0×10¹²ohm-centimeter, as measured by ASTM D-257; (ii) the composition has astatic decay rate of less than about 0.1 seconds from 1000 V to 100 V asmeasured at 50% relative humidity using a charged plate monitor; and inwhich said composition has a static decay rate of less than about 0.1seconds from 5000 V to 50 V or from −5000 V to −50 V as measured at 12%relative humidity by FTMS 101C.
 4. The composition of claim 1 whereinsaid composition has at least one of the following characteristics: (i)the composition has a hardness of at least 60 Shore A units, as measuredby ASTM D-2240; (ii) the composition has a tensile strength of at least10 MPa and an ultimate elongation of more than 300% as measured by ASTMD-412; (iii) the composition has Graves tear value of at least 5 kg/mm,as measured by ASTM D-624, using die C; (iv) the composition has a taberloss, per 1000 revolutions, of less than 100 mg, as measured by ASTMD-3389; (v) the composition has a weight average molecular weight of atleast 60,000; (vi) the composition has a melt flow index of less than50, as measured by ASTM D-1238 Procedure A at a barrel temperature of190° C. and a 3.8 kg piston load.
 5. The composition of claim 1 wherein(a), the polyester polyol component, is substantially free of polyetherpolyols.
 6. The composition of claim 1 further comprising at least onebase polymer.
 7. The composition of claim 6 wherein the base polymercomprises: a polyolefin; a styrenic; a thermoplastic polyurethane, apolyamide; an acrylic polymer; a polyvinylchloride, a chlorinatedpolyvinylchloride; a polyoxymethylene; a polyester; a polycarbonate; apolyphenylene oxide; polyphenylene sulfide; or combinations thereof. 8.A process of making an electrostatic dissipative thermoplasticpolyurethane composition, comprising the steps of: (i) reacting (a) atleast one polyester polyol intermediate comprising poly(diethyleneglycol adipate) with (b) at least one diisocyanate comprising4,4′-methylenebis-(phenyl isocyanate) and (c) at least one chainextender comprising hydroquinone di(hydroxyethyl) ether; (ii) adding tosaid electrostatic dissipative thermoplastic polyurethane an effectiveamount of a metal salt for electrostatic dissipation wherein said metalsalt is substantially free of any co-solvents and wherein the metal saltis not added to the electrostatic dissipative thermoplastic polyurethanecomposition in combination with a co-solvent; wherein the addition ofthe metal salt in step (ii) takes place after the reaction forming thethermoplastic polyurethane in step (i); wherein said metal saltcomprises lithium trifluoromethane sulfonamide; and wherein saidelectrostatic dissipative thermoplastic polyurethane composition furthercomprises an antistatic agent comprising tri-n-butylmethylammoniumbis-(trifluoroethanesulfonyl)imide.
 9. A shaped polymeric articlecomprising the electrostatic dissipative thermoplastic polyurethanecomposition of claim
 1. 10. The polymeric article of claim 9, whereinthe article comprises: packaging materials for ESD sensitivesemiconductor and electronic parts; durable or consumable parts forclean room equipment and applications; construction materials for cleanrooms and datacenters; fibers; laminated sheets; conveyor belts;pharmaceutical products; medical devices; electronic components;separators for use in the construction of lithium-ion batteries; polymerelectrolyte membranes for use in the construction of lithium-polymerbatteries and fuel cells; or combinations thereof.
 11. A battery partcomprising the electrostatic dissipative thermoplastic polyurethanecomposition of claim
 1. 12. An internal battery separator comprising theelectrostatic dissipative thermoplastic polyurethane composition ofclaim 1.